Speaker having a tubular pot



April 3, 1951 D. c. CARLSON SPEAKER HAVING A TUBULAR POT Filed Sept. 26, 1946 FlEil FlE. z

m 45 3 m3 o 3 m 5 2 7 2 am 1 A I l 1 1H awuc/vvtm DONALD C.CARL SON m QM I gy Patented Apr. 3, 1951 2,547,565 SPEAKER. HAVING A TUBULAR POT Donald C. Carlson, St. Paul, Minn., assignor to Wright Zimmerman, Inc., New Brighton, Minn., a corporation of Minnesota Application September 26, 1946, Serial No. 699,380

My invention rel-ates to an improvement in speakers and deals more particularly in a particular type of speaker pot designed to promote the efiiciency of the apparatus.

For many years efforts have been made to improve the efficiency of the metallic pot used to conduct magnetic lines of force from one end of a speaker magnet to a point adjacent the'other end thereof. The metallic pots previously used have been disadvantageous for certain definite reasons. In the first place these pots have usually been rectangular in shape. In bending the metal into rectangular form the structure of the metal is often broken at the corners, thus impeding the proper flow of electromagnetic force. Secondly 2 Claims. (Cl. 179-115.5)

these corners on the pot usually permit electromagnetic force to be emitted at the corners to c ecrease the effectiveness of the structure. Tests have shown that there is a considerable loss of elecromagnetic force at the corners of the usual rectangular speaker pot. Furthermore the pots made in the past have usually been made in a single strip which is electrically connected at the ends thereof. A considerable loss of magnetic force is usually experienced between the ends of the strip, thus also decreasing the efiiciency of the speaker. I

Efforts have been made to Weld the ends of the strip to provide a better electrical connection between the adjacent ends of the strip. This welding operation has often resulted in a change in the metallic structure of the strip tending to impede the passage of magnetic waves. Attempts have also been made to increase the size of the magnet and of the pot, but these increases result 'in' proportional increases'in the defects described. Attempts have also been made to form the speaker pots of a U-shaped strip of material, but such strips have proven inefficient in v actual use.

It is the object of the present invention to provide a speaker pot which is generally oval or ring-shaped and is formed of an integral piece of tubing or the like. Such a pot is provided with no sharp corners to emit electromagnetic waves and is formed with no seams through which the electromagnetic waves must pass. As a result high efficiency may be obtained with a minimum of cost.

A feature of the present invention lies in the fact that due to the efiiciency with which the electromagnetic waves may flow through the speaker pot, a minimum of electromagnetic force is lost and the efficiency of the speaker is considerably increased.

A further feature of the present invention resides in the provision of a speaker pot which may be formed of a short length of extruded metal which is generally oval in shape or may be formed by flattening the opposed sides of a short length of cylindrical seamless tubing. As a result my speaker pot may be formed at extremely low cost and is highly efficient. l

These and other objects and novel features of my invention will be more clearly and fully set forth in the following specification and claims.

In the drawings forming a part of my specification:

Figure l is a rear elevation view of my speaker showingthe construction thereof.

Figure 2 is a bottom plan view of my speaker showing the outline shape of the speaker pot.

Figure 3 is a cross sectional view through my speaker showing the construction thereof.

Figure 4 is a detail view of the speaker pot removed from the speaker.

The speaker A is formed as best illustrated in Figure 3 of the drawings. A flexible diaphragm lil formed of fibrous material is provided with a frusto-conical body ll terminating at its outer extremity in a'peripheral flange 12. A series of ring shaped corrugations I3 are provided in the flange 12 to permit ready flexibility of the diaphragm. A paper tube [4 is adhered to the rear surface of the frusto conical body I I in communication With a central aperture in the diaphragm ID. A speaker coil I5 encircles the paper sleeve l4 and is held thereon by a suitable film of cement or adhesive. The coil supporting sleeve IA is preferably of a single thickness of paper withinthe coil I5 and the coil itself is formed of extremely fine wire so that the entire sleeve I l and coil [5 are of but a thickness of a few thousandths of an inch.

A speaker frame [6 is connected to the diaphragm H) at the outer extremity thereof. This frame I6 is provided with a ring shaped outer extremity between opposite'sides of which extend an integral bridge portion H. The bridge portion [1 is off-set rearwardly from the marginal edge of the frame It? so as to lie rearwardly cf the frusto conical diaphragm body H. The center of the bridge portion ll of the frame is rearwardly bowed as indicated at l9 and is integrally attached to the speaker pct 20.

Thefispeaker pot 20 is generally oval in shape and comprises a seamless metal oval of the necessary width to properly conduct the flux from the permanent magnet. A magnet 2| which may be either of the permanent magnet type illustrated, or which may be an electromagnet, is secured to the inner surface of the speaker pot 20 along one flat side 22 thereof. The opposite fiat side 23 of the pct 20 is provided with an aperture 24 therethrough which aperture is of just sufficient diameter to accommodate the coil mounted upon the sleeve 14. The coil may move axially relative to the aperture 24, but is extremely close to the surface of the coil for maximum speaker efiiciency.

A pole piece 25 is supported at one end of the magnet 2|. This pole piece 25 is provided with an end 26 which is of proper diameter to fit within the sleeve [4. A gasket 21 is positioned between the pole piece 25 and the inner surface of the fiat side 23 of the pct 20. The end 26 of the pole piece 25 is concentric with the aperture 24 and provides a ring shaped aperture between the pole piece and the walls of the aperture 24 which is of just sufficient width to slidably support the sleeve [4 and its coil 15.

The speaker diaphragm I0 is provided with a. plug 29 of felt or suitable material for closing the central aperture thereof and to prevent dust and the like from entering the interior of the sleeve I l. A flexible diaphragm 30 also encircles the sleeve 14, being secured at its inner extremity to the diaphragm 10 adjacent the sleeve 14 and being secured at its inner extremity to the bridge I! of the frame 16. Thus the coil I5 is sealed from dust or dirt, while at the same time the diaphragm [0 may flex freely in an axial direction.

It will be seen that the rounded ends of the pot 20 conduct electronic magnetic waves with a minimum of loss. The flux from the end of the magnet abutting the flat side 22 is conducted to the opposite side 23 of the pot 20. There are no seams in the member 20 to interrupt the flow and as a result the efficiency of the speaker is substantially improved.

My speaker may be supported by suitable supporting screws or bolts extending through apertures such as 3| extending through the ring shaped outer frame IS. A relatively thick gasket 32 of paper or the like may be interposed between the speaker frame I6 and the panel against which the speaker is mounted. A bracket 33 may be provided on the bridge I! of the frame I6 on which the remaining structure of the speaker may be supported. The terminals of the coil 15 may be connected to bayonet type terminals 34 mounted on an insulation strip 35 on the bridge I1.

I have found that when a gap is provided in the speaker pot this gap effectively results in increasing the spacing between the pot and the magnet pole piece. By eliminating any such gap in the speaker pot, the effectiveness and efficiency of the speaker is greatly increased.

In accordance with the patent statutes, I have described the principles of construction and operation of my speaker, and while I have endeavored to set forth the best embodiment thereof, I desire to have it understood that obvious changes may be made within the scope of the following claims without departing from the spirit of my invention.

I claim:

1. A speaker including a speaker pot, said speaker pot comprising a short length of seamless tubing having a pair of substantially parallel side portions and integral arcuate curved ends connecting the same, a magnet secured to one of said fiat sides and extending toward the other, said magnet having a diameter slightly shorter than said parallel flat side portions, an aperture in the other of said sides in opposed relation to said magnet, a pole piece secured to said magnet and extending into said aperture in spaced relation to the walls thereof, and a hollow cylindrical gasket between said magnet and said other side wall.

2. A speaker comprising a speaker pot including a short length of seamless tubing having substantially parallel sides and integral arcuate ends, said flat sides being substantially equal in length to the diameter of said rounded ends, and an aperture through one of said fiat sides located centrally thereof, a magnet axially aligned with said aperture and engaging the other of said flat sides, a pole piece having a relatively large diameter and in contact with said magnet and a relatively small diameter end coaxial with, and extending into, said aperture, and a hollow cylindrical sleeve interposed between the large diameter end of said pole piece and said apertured side.

DONALD C. CARLSON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date Re. 22,017 Gaubert Feb. 3, 1942 1,941,476 Jensen Jan. 2, 1934 1,976,874 Brzeski Oct. 16, 1934 2,020,211 Quam Nov. 5, 1935 2,020,212 Quam Nov. 5, 1935 2,046,515 Jensen July 7, 1936 2,048,222 Rehmann July 21, 1936 2,141,595 Cornwell Dec. 27, 1938 2,426,948 Preston Sept. 2, 1947 2,458,158 Gilman Jan. 4, 1949 FOREIGN PATENTS Number Country Date 43,362 France May 11, 1934 351,723 Great Britain July 2, 1931 401,510 Great Britain Nov. 16, 1933 

